My guess is they will somehow implement a second crossbar.

Right now, you can get a crossbar with pressing both the shoulder buttons. In the future, I will hope we can have a combination of other buttons to bring up a new crossbar to complement new abilities.

Or a new way to cycle through your hotbars on the fly without breaking continuity. Maybe holding a button for an amount of time to change it to second hotbar, do your abilities and then release to get your initial hotbar again.

Yeah. Definitely will make me want to play with my 360 controller again.